RESUMO
The exceptionally high virulence of the West Nile NY99 strain makes its suitability in the development of a live WN vaccine uncertain. The aim of this study is to investigate the immunogenicity of noninfectious virus derivatives carrying pseudolethal mutations, which preclude virion formation without affecting preceding steps of the viral infectious cycle. When administered using DNA immunization, such constructs initiate an infectious cycle but cannot lead to a viremia. While the magnitude of the immune response to a noninfectious replication-competent construct was lower than that of virus or infectious DNA, its overall quality and the protective effect were similar. In contrast, a nonreplicating construct of similar length induced only a marginally detectable immune response in the dose range used. Thus, replication-competent noninfectious constructs derived from infectious DNA may offer an advantageous combination of the safety of noninfectious formulations with the quality of the immune response characteristic of infectious vaccines.
Assuntos
DNA Viral/imunologia , Vacinas de DNA/imunologia , Febre do Nilo Ocidental/prevenção & controle , Vacinas contra o Vírus do Nilo Ocidental/imunologia , Vírus do Nilo Ocidental/imunologia , Vírus do Nilo Ocidental/patogenicidade , Sequência de Aminoácidos , Animais , Animais não Endogâmicos , Anticorpos Antivirais/sangue , Chlorocebus aethiops , Cricetinae , Feminino , Humanos , Imunização , Camundongos , Dados de Sequência Molecular , Mutação , Testes de Neutralização , Plasmídeos , Recombinação Genética , Vacinas de DNA/administração & dosagem , Replicação Viral , Febre do Nilo Ocidental/imunologia , Febre do Nilo Ocidental/virologia , Vacinas contra o Vírus do Nilo Ocidental/administração & dosagem , Vírus do Nilo Ocidental/genéticaRESUMO
Recently, we have described a lineage 2 attenuated WN virus suitable for the development of a live WN vaccine. To design vaccine candidates with an improved immunogenicity, we assembled an infectious clone of the NY99 strain and created several chimeric constructs with reciprocal exchanges of structural protein genes between attenuated W956 and virulent NY99 and investigated their biological properties. Our data indicated that, while the growth rates of NY99 and chimeric viruses in tissue culture are determined primarily by properties of the structural proteins, determinants responsible for a highly cytopathic phenotype of NY99 or lack thereof for W956 are located within the nonstructural protein region of the WN genome. The high virulence of NY99 and the attenuated phenotype of W956 were found to be associated with determinants in the nonstructural region. Chimeric viruses carrying the NY99 structural proteins were attenuated in neuroinvasiveness and demonstrated an immunogenicity superior to W956.
Assuntos
Genes Virais , Recombinação Genética , Vírus do Nilo Ocidental/genética , Vírus do Nilo Ocidental/fisiologia , Animais , Anticorpos Antivirais/sangue , Chlorocebus aethiops , Efeito Citopatogênico Viral/genética , Modelos Animais de Doenças , Eletroforese em Gel de Poliacrilamida , Ensaio de Imunoadsorção Enzimática , Feminino , Dose Letal Mediana , Camundongos , Testes de Neutralização , Análise de Sobrevida , Células Vero , Proteínas não Estruturais Virais/genética , Proteínas não Estruturais Virais/fisiologia , Ensaio de Placa Viral , Proteínas Virais/análise , Proteínas Estruturais Virais/genética , Proteínas Estruturais Virais/fisiologia , Virulência/genética , Replicação Viral/genética , Vírus do Nilo Ocidental/imunologia , Vírus do Nilo Ocidental/patogenicidadeRESUMO
Seven volunteers involved in flavivirus studies have been immunized with commercial Japanese encephalitis and yellow fever vaccines JE-VAX and YF-VAX. Strong homologous and cross-reactive with West Nile virus (WNV) antibody responses with titers 1:1600 to 1:51200 were found in all donors. All donors developed high levels of yellow fever virus (YFV) and Japanese encephalitis virus (JEV) neutralizing antibodies with titers 1:50 to 1:1600 and 1:20 to 1:640, respectively, and WNV neutralizing antibodies with titers 1:10 to 1:80. In contrast, predominantly YF-specific cell-mediated immunity was detected in all immunized donors. Responses to YFV were long lasting, but the anti-JEV humoral immunity was found to decrease with time. Cross-reactive anti-WNV responses were following the same trend dropping below detectable level at 4 years post-immunization and sharply coming back after booster immunization with the JE vaccine. Thus, immunization with the commercial flavivirus JE vaccine may be beneficial for individuals at high risk of exposure to WNV, such as personnel involved in WN research.
Assuntos
Vacinas contra Encefalite Japonesa/imunologia , Febre do Nilo Ocidental/prevenção & controle , Vacina contra Febre Amarela/imunologia , Adulto , Anticorpos Antivirais/sangue , Reações Cruzadas , Feminino , Humanos , Imunização , Interferon gama/biossíntese , Masculino , Testes de Neutralização , Linfócitos T/imunologiaRESUMO
In a short time, West Nile virus has developed into a nationwide health and veterinary problem. The high virulence of the circulating virus and related lineage 1 WN strains hinders development of an attenuated live vaccine. We describe an attenuated WN isolate, WN1415, which is a molecularly cloned descendant of the WN prototype B956 strain. The parent virus belongs to lineage 2, members of which have not been associated with epidemic or epizootic outbreaks. A set of non-conservative mutations, mostly in non-structural protein genes, distinguishes the WN1415 isolate from the parent B956 prototype strain. Immunization with WN1415 (55-550,000 pfu) established a potent immunity, which protected the majority of mice against lethal challenge with WN NY99. The attenuated nature of the isolate and its excellent growth characteristics combined with the availability of a highly stable infectious clone make the isolate an attractive candidate for live WN vaccine development.
